594 PALAEONTOLOGY OF ILLINOIS. 



Position and locality: Warsaw beds. Abundant at Warsaw, 

 Illinois, and Monroe Co., Illinois; also in the St. Louis lime- 

 stone at Barrett's Station, St. Louis Co., Mo. 



POLYPORA SPININODATA Ulrich. 



PL LX, fig. 3. 



Of this species I have only seen one large semi-circular frond 

 in good preservation, and a smaller weather-worn fragment. 

 Unfortunately both adhere firmly to the rock so that the re- 

 verse only can be seen. With the aid of thin sections the 

 ranges of zooecia have been determined. The characters of the 

 reverse are as follows: Branches rather slender, varying from 

 0.3 to 0.6 or 0.7 mm., with thirteen to fifteen in 1 cm., bifur- 

 cating at long intervals. Their surface is strongly rounded, 

 covered with distinct longitudinal striations, and raised, at in- 

 tervals about equal to the length of a fenestrule, into pro- 

 nounced spines or nodes. Dissepiments generally less than half 

 the width of the branches, slightly depressed or on a level with 

 the branches, subcarinate or narrowly rounded. Fenestrules 

 elliptical, nine or ten in 1 cm., averaging 0.7 by 0.35 mm. 

 Zooecia at first in two ranges, then in three, and later on in 

 four. The last number prevails for from 1 to 3 mm. before the 

 branch divides. 



The strong hollow nodes on the reverse of the branches, dis- 

 tinguish this species from all Carboniferous species of Polypora 

 known to me. In the proportions and number of zooecia the 

 species occupies an intermediate portion between P. biseriata 

 and P. varsoviensis. Thin sections also show some slight dif- 

 ferences in their minute structure. 



Position and locality: Warsaw beds, at Warsaw, 111. 



POLYPORA CESTRIENSIS Dlrich. 



PI. LV, figs. 4-4b, and PL LX, flgs. 7-7c. 



Zoaria consisting of foliar expansions of somewhat lax and 

 irregular growth. Branches rather strong, slightly rounded, 

 with a row of faint nodes along the center about 0.5 mm, 

 apart; width above a bifurcation 0.5 mm., increasing to 1.0 

 mm., with about eight in 1 cm. Dissepiments slender, slightly 



